[Kea-users] Kea src IP incorrect

[Jason Lixfeld]

Hi,

I have a use case where requests are received on one interface, and responses are transmitted on another interface.  In ISC, this seems to have always worked as expected, but in Kea, it seems that responses are transmitted with the srcIP of the receiving interface, instead of the srcIP of the interface that is expected to transmit the response.

i.e.:

13:06:46.816502 IP (tos 0x0, ttl 253, id 48919, offset 0, flags [none], proto UDP (17), length 349)
    10.219.45.114.67 > 10.219.66.10.67: [udp sum ok] BOOTP/DHCP, Request from 00:01:47:2d:7a:d0, length 321, hops 1, xid 0x1e875e1f, Flags [none] (0x0000)
	  Gateway-IP 10.63.255.1
	  Client-Ethernet-Address 00:01:47:2d:7a:d0
	  Vendor-rfc1048 Extensions
	    Magic Cookie 0x63825363
	    DHCP-Message Option 53, length 1: Discover
	    Client-ID Option 61, length 8: "0298056"
	    Requested-IP Option 50, length 4: 10.63.255.84
	    Parameter-Request Option 55, length 14:
	      Subnet-Mask, Default-Gateway, Domain-Name-Server, Hostname
	      Domain-Name, BR, Lease-Time, DHCP-Message
	      Server-ID, TFTP, NTP, Time-Zone
	      Option 120, Classless-Static-Route
	    Vendor-Class Option 60, length 20: "ZNID-GE-2628A-00-0GN"
	    Agent-Information Option 82, length 21:
	      Circuit-ID SubOption 1, length 6: ^@^D^L7^B^B
	      Remote-ID SubOption 2, length 11: ^A^Irgw01.lab
	    END Option 255, length 0
13:06:46.824359 IP (tos 0x0, ttl 64, id 43882, offset 0, flags [DF], proto UDP (17), length 376)
    10.219.66.10.67 > 10.63.255.1.67: [bad udp cksum 0x579b -> 0x037e!] BOOTP/DHCP, Reply, length 348, hops 1, xid 0x1e875e1f, Flags [none] (0x0000)
	  Your-IP 10.63.255.84
	  Gateway-IP 10.63.255.1
	  Client-Ethernet-Address 00:01:47:2d:7a:d0
	  Vendor-rfc1048 Extensions
	    Magic Cookie 0x63825363
	    Subnet-Mask Option 1, length 4: 255.255.255.0
	    Domain-Name-Server Option 6, length 8: 66.207.192.4,206.223.173.6
	    Lease-Time Option 51, length 4: 60
	    DHCP-Message Option 53, length 1: Offer
	    Server-ID Option 54, length 4: 10.219.66.10
	    RN Option 58, length 4: 900
	    RB Option 59, length 4: 1800
	    Client-ID Option 61, length 8: "0298056"
	    TFTP Option 66, length 11: "10.63.255.1"
	    Classless-Static-Route Option 121, length 16: (10.32.0.0/24:10.63.255.1),(10.32.11.0/24:10.63.255.1)
	    Agent-Information Option 82, length 21:
	      Circuit-ID SubOption 1, length 6: ^@^D^L7^B^B
	      Remote-ID SubOption 2, length 11: ^A^Irgw01.lab
	    END Option 255, length 0

root at kea1:/usr/local/etc/kea# ip route
default via 10.219.66.1 dev ens32 onlink
10.32.0.0/11 dev ens34 scope link
10.32.0.32/28 dev ens34 proto kernel scope link src 10.32.0.40
10.219.66.0/24 dev ens32 proto kernel scope link src 10.219.66.10
root at kea1:/usr/local/etc/kea#

OFFER is being sent to 10.63.255.1, but sourced from 10.219.66.10, when it should be sourced from 10.32.0.40.

I can’t seem to adjust option 54 to force the server ID (which may be the whole issue to begin with?):

2017-09-13 13:31:33.238 DEBUG [kea-dhcp4.bad-packets/522] DHCP4_PACKET_DROP_0007 [hwtype=1 00:01:47:2d:7a:d0], cid=[00:30:32:39:38:30:35:36], tid=0x52055156: failed to process packet: Option 54 already present in this message.

{
        "client-class" : "rgw01.lab",
        "subnet": "10.63.255.0/24",
        "valid-lifetime": 60,
        "option-data": [
                {
                        "name": "domain-name-servers",
                        "code": 6,
                        "space": "dhcp4",
                        "csv-format": true,
                        "data": "66.207.192.4, 206.223.173.6"
                },
                {
                        "name": "tftp-server-name",
                        "data": "10.63.255.1"
                },
                {
                        "name" : "dhcp-server-identifier",
                        "code" : 54,
                        "space" : "dhcp4",
                        "csv-format" : true,
                        "data" : "10.63.255.1"
                },
                {
                        "name": "classless-static-routes",
                        "data": "180A20000A3FFF01180A200B0A3FFF01"
                }
        ],
        "pools": [
                {
                        "pool": "10.63.255.2 - 10.63.255.254"
                }
        ],
        "reservations": [
                {
                        "flex-id": "010972677730312e6c616200040c370201",
                        "ip-address": "10.63.255.69",
                        "boot-file-name": "byor/26xx_current/S0300608"
                }
        ]
}


Any pointers?

Thanks!